Meeting Report - February 2010

For a moment in time, 40 members and guests gathered on February 23, 2010,
in the auditorium at Dolby Labs in Burbank, CA to hear a talk by SMPTE
Fellow Al Kovalick of Avid Technology. He presented  "A Brief History of the
Second". Al developed several themes centered on the second and its
relationship to media systems. Although we often take for granted the tick
of the clock, the second has deep mechanical, electrical, atomic,
relativistic, astronomical, and poetic meaning. The talk was divided into
several parts: the basics of timekeeping; defining "the second,  Einstein's
theory of Special and General Relativity as relates to time dilation; atomic
clocks; time systems and their applications to video production and
distribution.
 
The discussion included "Greenwich time balls", the all-important work to
navigation of clock inventor John Harrison, who strove to win the Longitude
Prize of 1712, Cesium clocks, ensemble clocks,  UTC/TAI, GPS, and their
ultimate connection to video systems timing.
 
The audience had fun with an interactive demo of the physical "ensemble
clock" or paper clock. At a known reference time, Al asked 8 people to write
on cards the exact time displayed on their wrist watches. Paul Chapman,
section Chair, averaged the results and derived a new "ensemble time", an
average that was nearly the same as the target time and more improved, on
average, than any individual wrist watch time value. Instructive.
 
Al discussed that leap seconds are necessary to align atomic clocks to the
actual rotation rate of the earth. The earth does not rotate precisely at 24
hours (solar mean time) but rotates, instead, on its axis every 86,400.002
seconds, slightly more than 24 hours. So in a given year, this 2 Ms offset
adds up to ~730 Ms. Hence, leap seconds are needed to keep earth time and
atomic time in alignment. There is always a small known offset between
atomic and earth time, but less than one second.
 
 SMPTE has been in the "time business" for half a century. Al described the
recent work of the SMPTE/EBU Task Force on Timing and Synchronization. SMPTE
has formed a new Standards Committee (33TS) to create a new sync signal and
time label.  The current black-burst reference signal will be replaced with
a new sync signal locked to GPS time. Any framing signal, regardless of
frame rate and resolution, can be created within the media facility with
precise horizontal and vertical timing relationships.

Al Kovalick serves as a Strategist and Fellow with Avid Technology, and is
also the author of "Video Systems in an IT Environment".

Submitted,
Paul Chapman - Chair, Hollywood Section.